Electronic flashes provide supplemental light for photography to enhance images captured by a camera or other imaging devices. Traditional electronic flashes utilize a bulb filled with gas, such as argon, krypton, neon and xenon, or vapor, e.g., mercury vapor. When a high voltage is applied to the bulb, the gas or vapor is ionized, allowing electrons to flow through the gas or vapor. These electrons excite the atoms of the gas or vapor, which emit light. The wavelength characteristics of the emitted light depends on the gas or vapor in the bulb. In the case of mercury vapor, the emitted light is ultraviolet light, which is usually converted to visible light using fluorescent material since ultraviolet light is typically not desired.
Recently, light emitting diodes (“LEDs”) have been improved to a point with respect to operating efficiency where LEDs are now replacing conventional light sources, even bulbs in electronic flashes. A typical LED flash includes one or more LED dies and a lens. The LEDs are attached or mounted onto a substrate within a reflector cup, which reflects the light emitted from the LEDs toward a desired direction. The lens is positioned over the reflector cup to channel the emitted light to a sixty-degree (60°) viewing angle to match the viewing angle of the camera.
As illustrated in FIG. 1, a concern with conventional LED flashes is that the radiation pattern 10 of flashes of light produced by the LED flashes is round or oval. However, the imaging field of view 12 of a camera is rectangular. Since the imaging field of view 12 needs to be within the radiation field 10, a significant portion of the emitted light from the conventional LED flashes is not used when capturing an image of a scene of interest. Thus, flashes of light produced by conventional LED flashes cannot be used efficiently when capturing rectangular images.
In view of this concern, there is a need for an LED flash and method for producing a flash of light that allows the flash of light to be used efficiently by an imaging device, such as a digital camera.